I've been asked many times do I really have 325/50/15's on my monte and how did I get them to fit...when I say fit I mean even with the car sitting low in back, with the tires tucked up inside the wheel lip.
I have had this set-up on my car for over 5 years and it has never hit the lip...granted the lip is trimmed which will be necessary to use these tires. The inner sidewall will rub on the frame on very hard cornering or entering an steep angled drive...you will hear a squeek but no harm is done as the frame is smooth and the tire is just rubbing. One thing to point out here...this set-up is just for the cool factor of such a fat tire and the same traction results could achieved using a narrower tire.
A 325/50 has roughly a 13" section width on a 10" rim...now there is no way it will fit with that rim. You must use a 8" rim to shrink the sidewall down...which will bring it down 8/10". It will not even work with an 8 1/2" rim...I tried.
You will need a rim with 5" of back spacing and you still will have to use a 1/4" spacer. I have since purchased aftermarket axles (Moser) that are 1/4" thicker than stock axles which solved my spacer problem (racing with a spacer is not suggested).
Trimming or grinding the lip is necessary and can be trimmed a little at a time when trial fitting. Another thing to point out is your rearend must be perfectly centered...I have all aftermarket suspension parts and poly bushings to prevent any slop with side to side movement.
The inner wheel housing will need to be massaged away from the tire...this will be self explanatory when you trial fit the tire and see where you are close. I used a mallet and you can not even tell that it has been altered when looking at it.
You can see in the first photo how close it will be to the frame (the daylight is the gap that you will have), it is a 1/4" to 3/8"...you see what I mean when I say you have to follow exactly what I did or it will not fit.
the second photo shows a view as though you were looking straight up at the lip and tire sidewall...there is a safe 1/2" of clearance there. I have my lip ground as far as you would want to go...the welded seam would be affected if you went any further...I then used por-15 on the ground area to prevent any possible chance of rust.
With all that being said I would do it slightly different next time...I would use a wheel with alot less b.s. for a deep dish look and have the rearend built (narrowed) around the wheels. This would look so much cooler (in my opinion) when seeing such a deep looking wheel (even though it would still be an 8" rim) it would appear or give the illusion of a fatter wheel and a mini tubbed look.